(113)B和(100)面InAs/GaAs量子点光致发光光谱特性研究

利用分子束外延技术在(100)和(113)B GaAs衬底上进行了有/无AlAs盖帽层量子点的生长,测量了其在4～100 K温度区间的PL光谱。通过对PL光谱的积分强度、峰值能量和半高宽进行分析进而研究载流子的热传输特性。无AlAs盖帽层的(113)B面量子点的PL光谱的热淬灭现象可以由载流子极易从量子点向浸润层逃逸来解释。然而,有AlAs盖帽层的(113)B量子点的PL热淬灭主要是由于载流子进入了量子点与势垒或者浸润层界面中的非辐射中心引起的。并且其PL的温度依存性与利用Varshni定律计算的体材料InAs的温度依存性吻合很好,表明载流子通过浸润层进行传输受到了抑制,由于AlAs引起的相分离机制(113)B量子点的浸润层已经消失或者减小了。(100)面有AlAs盖帽层的PL半高宽的温度依存性与无AlAs盖帽层的量子点大致相同,表明在相同外延条件下相分离机制在(100)面上不如(113)B面显著。     

生长在Ge_xSi_（1－x）（001）衬底上应变GaAs层的光学性质

采用紧束缚方法计算了生长在ＧｅｘＳｉ１－ｘ（００１）衬底上的应变ＧａＡｓ层带间光跃迁的振子强度以及三次非线性光极化率，讨论了振子强度及三次非线性光极化率随衬底合金组分ｘ的变化关系。计算结果表明：对所有ｘ值，及随ｘ的变小而变小；及随ｘ的变小而变大。对ｎ型ＧａＡｓ／ＧｅｘＳｉ１－ｘ（００１），应变使和变小；对ｐ型ＧａＡｓ／ＧｅｘＳｉ１－ｘ（００１），应变使变大，但使变小。     

Photoluminescence Studies of Si-Doped Epitaxial GaAs Films Grown on (100)- and (111)A-Oriented GaAs Substrates at Lowered Temperatures

The electrical properties and photoluminescence features of uniformly Si-doped GaAs layers grown on GaAs substrates with the (100) and (111)A crystallographic orientations of the surface are studied. The samples are grown at the same As₄ pressure in the growth temperature range from 350 to 510°C. The samples grown on GaAs(100) substrates possess n-type conductivity in the entire growth temperature range, and the samples grown on GaAs(111)A substrates possess p-type conductivity in the growth temperature range from 430 to 510°C. The photoluminescence spectra of the samples exhibit an edge band and an impurity band. The edge photoluminescence band corresponds to the photoluminescence of degenerate GaAs with n- and p-type conductivity. The impurity photoluminescence band for samples on GaAs(100) substrates in the range 1.30–1.45 eV is attributed to V_As defects and Si_As–V_As defect complexes, whose concentration varies with sample growth temperature. Transformation of the impurity photoluminescence spectra of the samples on GaAs(111)A substrates is interpreted as being a result of changes in the V_As and V_Ga defect concentrations under variations in the growth temperature of the samples.     

室温下脉冲激光沉积制备高取向度AlN薄膜

用脉冲激光沉积(PLD)方法,在p-Si(100)衬底上、室温下和不同N2氛围中制备了高度取向的AlN薄膜,并利用X射线衍射(XRD)仪、傅立叶变换红外(FTIR)光谱仪和扫描电子显微镜(SEM)对样品的特征进行了研究.结果表明,在从5×10-6～5.0 Pa的N2气压范围内,制备的薄膜都呈现h＜100＞晶向,并且随着气压的升高,样品的结晶度有明显的提高.另外,随着N2浓度的增大,Al-N键的结合度增强,AlN晶粒的尺寸增大,在样品表面出现杂散晶粒,薄膜的粗糙度增大.     

Terahertz Emission from GaAs Films on Si(100) and Si(111) Substrates Grown by Molecular Beam Epitaxy

We report on the terahertz emission from femtosecond-laser-irradiated GaAs layers grown on Si(100) and Si(111) substrates. The results show that the terahertz emission from GaAs on Si is stronger than that of a semi-insulating bulk GaAs crystal. This increase is attributed to the strain field at the GaAs/Si interface. In the GaAs of the Si(100) sample, the stronger terahertz emission is observed compared with GaAs on Si(111). Moreover, the effect of changing the doping type of the Si substrate from n-type to semi-insulating was also studied and it was found that the terahertz emission intensity of GaAs on semi-insulating Si(100) is stronger than that of GaAs on n-type Si(100). Finally, strong terahertz emission from GaAs on semi-insulating Si(100) was observed not only in the reflection geometry but also in the transmission geometry. These results hold promise for new applications of terahertz optoelectronics.     

Electrical and Photoluminescence Studies of {LT-GaAs/GaAs:Si} Superlattices Grown by MBE on (100)- and (111)A-Oriented GaAs Substrates

Semiconductors - The results of studying semiconductor structures proposed for the first time and grown, which combine the properties of LT-GaAs with p-type conductivity upon doping with Si, are...     

Influence of Substrate Misorientation on the Composition and the Structural and Photoluminescence Properties of Epitaxial Layers Grown on GaAs(100)

The influence of the degree of misorientation and treatment of a GaAs substrate on the structural and optical characteristics of homoepitaxial GaAs/GaAs(100) structures grown by metal–organic chemicalvapor deposition is studied. From the data obtained by a series of structural and spectroscopic techniques, it is shown that the degree of deviation of the substrate from the exact orientation towards the [110] direction by an angle of up to 4° brings about stepwise growth of the GaAs film in the initial stage and a further increase in the degree of misorienration towards the [110] direction to 10° results in an increase in the number of structural defects in the epitaxial film. At the same time, the samples of homoepitaxial structures grown by metal–organic chemical-vapor deposition on GaAs(100) substrates misoriented by 4° towards the [110] direction possess the highest photoluminescence efficiency; it is ~15% higher than the corresponding quantity for structures grown on precisely oriented GaAs(100) substrates. Preliminary polishing of the GaAs substrate (removal of an oxide layer) also yields the intensification of photoluminescence emission compared to emission in the case of an unpolished substrate of the same type. For samples grown on substrates misoriented by 4°, such an increase in the photoluminescence efficiency is ~30%.     

The Growth of InAsxSb1 –x Solid Solutions on Misoriented GaAs(001) Substrates by Molecular-Beam Epitaxy

Semiconductors - The effect of a substrate misorientation degree from a singular face on the composition and morphology of layers of InAsxSb1 –x solid solutions obtained by molecular-beam...     

TEM Characterization of HgCdTe/CdTe Grown on GaAs(211)B Substrates

A microstructural study of HgCdTe/CdTe/GaAs(211)B and CdTe/GaAs(211)B heterostructures grown using molecular beam epitaxy (MBE) was carried out using transmission electron microscopy and small-probe microanalysis. High-quality MBE-grown CdTe on GaAs(211)B substrates was demonstrated to be a viable composite substrate platform for HgCdTe growth. In addition, analysis of interfacial misfit dislocations and residual strain showed that the CdTe/GaAs interface was fully relaxed except in localized regions where GaAs surface polishing had caused small pits. In the case of HgCdTe/CdTe/GaAs(211)B, the use of thin HgTe buffer layers between HgCdTe and CdTe for improving the HgCdTe crystal quality was also investigated.     

超晶格GaAs/(GaAl)As(100)和GaAs/Ge(100)的电子结构

本文采用经验紧束缚方法,计算了第一类半导体超晶格(GaAs)_(nl)/(Ga_xAl_(1-x)As)_(n2)(100)和(GaAs_n/(Ge)_n(100)的电子结构。对于GaAs/(GaAl)As,得到了能带边随层数(n_1,n_2)变化的关系及带边电子态的空间分布,并得出能隙随n和组分x的变化(n_1=n_2=n≤10),结果与现有实验值和其它理论计算基本相符;对于GaAs/Ge,计算了GaAs和Ge等厚时,间接能隙随层数的变化,考察了(GaAs)_5/(Ge)_5(100)的能带结构。在两种超晶格中,本文都报道了界面态的存在,讨论了超晶格的准二维性质。     

在（311）面上所生长的Al_xGa_（1－x）As／GaAs单量子阱特性

文章报道了用分子束外延（ＭＢＥ）法在６００℃和６５０℃下，在Ｓｉ掺杂的ＧａＡｓ衬底的（３１１）Ａ和（３１１）Ｂ面上成功地生长了高质量的ＡｌｘＧａ１－Ａｓ／ＧａＡｓ单量子阱材料。计算了光荧光（ＰＬ）峰值能量，并与实验作了比较。讨论了（３１１）Ａ和（３１１）Ｂ面上的不同生长特性。     

Si(111)衬底上生长的GaN的形貌与AlN缓冲层生长温度的关系

利用LP-MOCVD技术在Si(111)衬底上,用不同温度生长AlN缓冲层,再在缓冲层上外延GaN薄膜.采用高分辨率双晶X射线衍射(DCXRD)技术和扫描电子显微镜(SEM)分析这些样品,比较缓冲层生长温度对缓冲层和外延层的影响,并提出利用动力学模型解释这种温度的影响.进一步解释了GaN外延层表面形貌中"凹坑"的形成及"凹坑"与缓冲层生长温度的关系.结果表明,温度的高低通过影响缓冲层初始成核密度和成核尺寸来影响外延层表面形貌.     

分子束外延GaAs/Si应变层的光致发光和光反射谱研究

研究了分子束外延GaAs/Si光致发光谱的激发强度和温度依赖关系。确定出2个本征发光峰,分别对应于导带至m_J=±3/2和m_J=±1/2价带的复合。这种价带的移动和分裂归因于由GaAs和Si的热膨胀系数不同所引起的GaAs层双轴张应力。还观测到4个非本征发光峰,分别为导带至m_J=±1/2碳受主态发光、可能与缺陷有关的发光以及可能由Mn和Cu受主杂质引起的发光。室温下将GaAs/Si和GaAs/GaAs材料的光反射谱进行比较,前者明显向低能移动约8meV,观测到3个特征谱结构,与光致发光结果相一致。     

Si(111)衬底上生长的GaN的形貌与AlN缓冲层生长温度的关系

利用LP-MOCVD技术在Si（111）衬底上,用不同温度生长AlN缓冲层,再在缓冲层上外延GaN薄膜．采用高分辨率双晶X射线衍射（DCXRD）技术和扫描电子显微镜（SEM）分析这些样品，比较缓冲层生长温度对缓冲层和外延层的影响，并提出利用动力学模型解释这种温度的影响．进一步解释了GaN外延层表面形貌中“凹坑”的形成及“凹坑”与缓冲层生长温度的关系．结果表明，温度的高低通过影响缓冲层初始成核密度和成核尺寸来影响外延层表面形貌．     

Molecular-Beam Epitaxy of Two-Dimensional GaSe Layers on GaAs(001) and GaAs(112) Substrates: Structural and Optical Properties

Semiconductors - The results of studies of the structural and optical properties of two-dimensional GaSe layers grown by molecular-beam epitaxy on GaAs(001) and GaAs(112) substrates using a valve...     

(100),(111)B InP衬底上InGaAsP相图的计算

本文运用DLP模型计算了与(100),(111)B InP衬底晶格匹配的In_xGa_(1-x)As_yP_(1-y)相图。计算表明,根据DLP模型原理,对K值加以取向修正后,DLP模型可以描述不同取向InP衬底上InGaAsP体系的相平衡。     

Effect of In Situ Thermal Cycle Annealing on GaN Film Properties Grown on (001) and (111) GaAs, and Sapphire Substrates

The effect of in-situ thermal cycle annealing (TCA) has been investigated for GaN growth on GaAs(lOO), GaAs(111) and sapphire substrates. X-ray diffractometry (XRD) and surface morphology studies were performed for this purpose. Enhanced cubic phase characteristics were observed by employing annealingfor GaN layers grown on (001) GaAs. The thickness of the layer subject to annealing is critical in determining the phase of the subsequently grown layer. Thin initial layers appear to permit maintenance of the cubic phase characteristics shown by the substrate, while hexagonal phase characteristics are manifested for thick initial layers. Higher temperature of annealing of thick pre-annealed layers results in changes from mixed cubic/hexagonal phase to pure hexagonal phase. Growth on GaAs(111) substrates showed single cubic phase characteristics and similar enhancement of crystal quality by using TCA as for layers on GaAs(OOl). Micro-cracks were found to be present after TCA on GaAs(lll) substrates. Thermal cycling also appears to be beneficial for layers grown on sapphire substrates.     

Photoreflectance Spectroscopy Study of LT-GaAs Layers Grown on Si and GaAs Substrates

The mechanical strains and densities of surface charge states in GaAs layers grown by low-temperature (LT) molecular-beam epitaxy on Si(100) and GaAs(100) substrates are investigated by photoreflectance spectroscopy. Lines corresponding to the fundamental transition (E _g ) and the transition between the conduction band and spin-orbit-split valence subband (E _g + Δ _SO ) in GaAs are observed in the photoreflectance spectra of Si/LT-GaAs structures at 1.37 and 1.82 eV, respectively. They are shifted to lower and higher energies, respectively, relative to the corresponding lines in GaAs/LT-GaAs structures. Comparing the spectra of the Si/LT-GaAs and GaAs/LT-GaAs structures, it is possible to estimate mechanical strains in LT-GaAs layers grown on Si (by analyzing the spectral-line shifts) and the density of charge-carrier states at the GaAs/Si heterointerface (by analyzing the period of Franz–Keldysh oscillations).     

生长在In_xGa_（1－x）As（001）衬底上应变薄层GaAs的电子能带结构

采用经验的紧束缚方法对生长在ＩｎｘＧａ１－ｘＡｓ（００１）衬底上的应变薄层ＧａＡｓ的电子能带结构进行了计算。应变对能带结构的影响按标度定则进行计算，其中标度指数根据对畸变势常数的实验值进行拟合而确定。给出了ＧａＡｓ／ＩｎｘＧａ１－ｘＡｓ（００１）能带结构随衬底合金组分ｘ的变化关系，讨论了应变对能带色散关系的影响。